A systematic histologic analysis of nonablative laser therapy in a porcine model using the pulsed dye laser.

BACKGROUND To our knowledge, no systematic analysis of nonablative laser therapy has been performed. OBJECTIVE To alter the parameters (fluence, spot size, pulse duration, and use of cooling spray) for the pulsed dye laser to determine the precise settings that would yield the most favorable dermal remodeling in a porcine model. METHODS Research was conducted in an animal laboratory at Albany Medical College. An anesthetized Yucatan miniature pig was subjected to a pulsed dye laser at various parameters. After 10 weeks, the laser-treated areas were harvested and processed for blinded, randomized, histologic evaluation. Negative (nontreated skin) and positive (ablative carbon dioxide laser-treated skin) controls were compared with the nonablative pulsed dye laser-treated areas. MAIN OUTCOME MEASURES Quantitative assessment of collagen band width and cells per high-power field and qualitative assessment of epidermal and dermal changes. RESULTS A significant difference (P<.001) in collagen band width was evident when nonablative laser-treated skin and carbon dioxide ablative laser-treated skin specimens were compared with untreated skin specimens, but no significant (P =.18) difference existed between the nonablative and ablative modalities. Similarly, cellular hypertrophy, as measured by high-power field, corroborated the previous findings. Furthermore, a higher fluence, a larger spot size, and a longer pulse duration proved statistically significant for increased collagen band width (P =.01, P<.001, and P<.001, respectively), and a larger spot size and a longer pulse duration exhibited significance for cells per high-power field (P =.02 and P =.009, respectively), with a trend toward significance for higher fluence (P =.09). Overall, the dermis was considerably thicker for nonablative and ablative laser-treated areas compared with untreated skin, but this could not be quantified because the depth exceeded the punch biopsy instrument. The epidermis remained unchanged. CONCLUSIONS The nonablative pulsed dye laser has demonstrated favorable histologic evidence of dermal remodeling, and its effects were similar to histologic changes seen with the carbon dioxide ablative laser, both of which were statistically significant compared with untreated skin, as seen in this preliminary animal model.